The definition of the word "steel" has been the subject of a scientific
quarrel on account of new processes. The grand distinguishing trait of
steel, to which it owes all the qualities that make it valuable for the
uses to which no other metal can be put, is _homogeneity due to
fusion_. Wrought iron, while having similar chemical qualities, and
often as much carbon, is _laminated in structure_. Structural
qualities are largely increasing in importance, and as the structural
compounds came gradually to be produced more and more by the casting
processes; as they ceased to be laminated in structure and became
homogeneous, they were called by the name of steel. The name has been
based upon the structure of the material rather than upon its chemical
ingredients as heretofore. There is now a disposition to call all
compounds of iron that are crystalline in structure, made homogeneous by
casting, by the general name of steel, and to distinguish all those
whose structural quality is due to welding by the name of iron.
[Footnote: It should be understood that the shapes of structural and
other forms of what we now call steel are given by rolling the ingot
after casting, and that the crystalline composition of the metal
remains.] This is an outline of the controversy about the differences
which should be expressed by a name, between tool steel and structural
steel. In tool steel there is an almost infinite variety as to quality.
The best is a high product of practical science, and how to make the
best seems now, as hinted above, a lost art. It has, besides, a great
variety. These varieties are only produced after thousands of
experiments directed to finding out what ingredients and processes make
toward the desired result. These processes, were they all known outside
the manufactories of certain specialists, would little interest the
general reader. All machinists know of certain brands of tool steel
which they prefer. Tool steel is made especially for certain purposes;
as for razors and surgical instruments, for saws, for files, for